Cytokine-induced increases in ADAMTS-4 mRNA expression do not lead to increased aggrecanase activity in ADAMTS-5-deficient mice.
Summary of "Cytokine-induced increases in ADAMTS-4 mRNA expression do not lead to increased aggrecanase activity in ADAMTS-5-deficient mice."
: To compare the regulation of aggrecanase mRNA and enzyme activity by pro-inflammatory cytokines in primary mouse chondrocytes.
: Primary chondrocytes were isolated from knee epiphyses of 6-day old mice and cultured as monolayers. The cells were incubated with either tumor necrosis factor-alpha (TNF-alpha), oncostatin M (OSM) or interleukin-6/soluble interleukin-6 receptor (IL-6/sIL-6R), and mRNA levels measured by quantitative PCR at various time points. To measure aggrecanase activity the cells were incubated with cytokine in the presence of exogenous aggrecan, and substrate cleavage was measured using neo-epitope antibodies.
: Expression of both ADAMTS-4 and ADAMTS-5 mRNAs was up-regulated by TNF-alpha and OSM. ADAMTS-5 mRNA expression was also up-regulated by IL-6. Treatment of wildtype chondrocytes with each of the three cytokines increased cleavage of aggrecan at Glu(373) downward arrow(374)Ala and Glu(1670) downward arrow(1671)Gly; in chondrocytes lacking ADAMTS-5 activity there was negligible cleavage at either site despite an increased expression of ADAMTS-4 mRNA. None of the cytokines substantially altered mRNA expression of ADAMTS-1 or ADAMTS-9.
: Despite substantial increases in the expression of ADAMTS-4 mRNA induced by TNF-alpha and OSM, these cytokines induced little, if any increase in aggrecanolysis in ADAMTS-5-deficient chondrocytes. Our data shows a poor correlation between the level of cytokine-induced ADAMTS-4 mRNA expression and the level of aggrecan-degrading activity in cultured chondrocytes.
University of Melbourne Department of Paediatrics and Murdoch Childrens Research Institute, Royal Children's Hospital, Melbourne, Victoria, 3052, Australia.
This article was published in the following journal.
Name: Arthritis and rheumatism
Medical and Biotech [MESH] Definitions
Suppressor Of Cytokine Signaling Proteins
A family of structurally related proteins that are induced by CYTOKINES and negatively regulate cytokine-mediated SIGNAL TRANSDUCTION PATHWAYS. SOCS proteins contain a central SH2 DOMAIN and a C-terminal region of homology known as the SOCS box.
A gene silencing phenomenon whereby specific dsRNAs (RNA, DOUBLE-STRANDED) trigger the degradation of homologous mRNA (RNA, MESSENGER). The specific dsRNAs are processed into SMALL INTERFERING RNA (siRNA) which serves as a guide for cleavage of the homologous mRNA in the RNA-INDUCED SILENCING COMPLEX. DNA METHYLATION may also be triggered during this process.
Cytokine Receptor Gp130
A cytokine receptor that acts through the formation of oligomeric complexes of itself with a variety of CYTOKINE RECEPTORS.
Heterogeneous-nuclear Ribonucleoprotein K
A heterogeneous-nuclear ribonucleoprotein found in the CELL NUCLEUS and the CYTOPLASM. Heterogeneous-nuclear ribonucleoprotein K has been implicated in the regulation of gene expression at nearly all levels: GENETIC TRANSCRIPTION; mRNA processing (RNA PROCESSING, POST-TRANSCRIPTIONAL), mRNA transport, mRNA stability, and translation (TRANSLATION, GENETIC). The hnRNP protein has a strong affinity for polypyrimidine-rich RNA and for single-stranded polypyrimidine-rich DNA. Multiple hnRNP K protein isoforms exist due to alternative splicing and display different nucleic-acid-binding properties.
Stat Transcription Factors
A family of transcription factors containing SH2 DOMAINS that are involved in CYTOKINE-mediated SIGNAL TRANSDUCTION. STAT transcription factors are recruited to the cytoplasmic region of CELL SURFACE RECEPTORS and are activated via PHOSPHORYLATION. Once activated they dimerize and translocate into the CELL NUCLEUS where they influence GENE expression. They play a role in regulating CELL GROWTH PROCESSES and CELL DIFFERENTIATION. STAT transcription factors are inhibited by SUPPRESSOR OF CYTOKINE SIGNALING PROTEINS and PROTEIN INHIBITORS OF ACTIVATED STAT.
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